Field of the Invention
The invention relates to an air-intake device having a variable induction-pipe length for an internal combustion engine, including a cylindrical collector, induction pipes disposed on a periphery of the collector, lead-in ports to the induction pipes, and a switching device in the shape of a cylinder sector, the switching device pivotably mounted for closing the lead-in ports in a first rotary position and opening the lead-in ports in a second rotary position.
Accordingly, the invention is directed toward variable induction pipes of an internal combustion engine, i.e. induction pipes adjustable between two lengths, wherein the length of the induction pipes is adapted in each case to the operating state of the internal combustion engine. The respective maximum engine output can thereby be increased at both low and high rotational speeds.
International Publication No. WO 96/02743, corresponding to U.S. Pat. No. 5,709,182, describes an air-intake device which has a collector with a cylindrical construction and induction pipes disposed on the periphery thereof. The induction pipes are connected to the collector at one end through inlets. However, they may also communicate directly with the collector through lead-in ports, with the effective length of the induction pipes then being reduced. The effective length of the induction pipes denotes the length of an induction-pipe region in which most of the air mass flow occurs.
A switching device which has a cylindrical construction is pivotably mounted in the collector. It closes the lead-in ports in a first rotary position. To that end, it bears on an encircling extension of the lead-in ports in a two-dimensional manner. In the first rotary position, the effective induction-pipe length then only corresponds to the length of the induction pipe from the entry up to the cylinder of the internal combustion engine, if the lead-in port is tightly closed. Considerable outlay is therefore necessary in order to keep the tolerances in the switching device and in the collector so low that bearing of the switching device in a sealing manner against the encircling extension is ensured.